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Fix conversion from Categorical to pa.dictionary in read_parquet #10285

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merged 5 commits into from
May 16, 2023
Merged

Fix conversion from Categorical to pa.dictionary in read_parquet #10285

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96c5d1e
Fix conversion from ``Categorical`` to ``pa.dictionary`` in ``read_pa…
phofl May 15, 2023
d3f3be9
Fix
phofl May 15, 2023
f7615bb
Update test_parquet.py
phofl May 16, 2023
ae37409
Merge remote-tracking branch 'upstream/main' into read_parquet_cat
phofl May 16, 2023
15e9cc3
Adjust test
phofl May 16, 2023
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4 changes: 3 additions & 1 deletion dask/dataframe/io/parquet/arrow.py
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Original file line number Diff line number Diff line change
Expand Up @@ -1256,7 +1256,9 @@ def _create_dd_meta(cls, dataset_info):
# Make sure all categories are set to "unknown".
# Cannot include index names in the `cols` argument.
meta = clear_known_categories(
meta, cols=[c for c in categories if c not in meta.index.names]
meta,
cols=[c for c in categories if c not in meta.index.names],
dtype_backend=dtype_backend,
)

if partition_obj:
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12 changes: 12 additions & 0 deletions dask/dataframe/io/tests/test_parquet.py
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Expand Up @@ -4904,3 +4904,15 @@ def test_read_parquet_preserve_categorical_column_dtype(tmp_path):
index=[0, 0],
)
assert_eq(ddf, expected)


@PYARROW_MARK
@pytest.mark.skipif(not PANDAS_GT_150, reason="Requires pd.ArrowDtype")
def test_dtype_backend_categoricals(tmp_path):
df = pd.DataFrame({"a": pd.Series(["x", "y"], dtype="category"), "b": [1, 2]})
outdir = tmp_path / "out.parquet"
df.to_parquet(outdir, engine="pyarrow")
ddf = dd.read_parquet(outdir, engine="pyarrow", dtype_backend="pyarrow")
pdf = pd.read_parquet(outdir, engine="pyarrow", dtype_backend="pyarrow")
# Set sort_results=False because of pandas bug
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Is there an upstream issue for this?

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My pr was already merged, will update tomorrow when nightlies are available

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@phofl phofl May 15, 2023 •
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pandas-dev/pandas#53232

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Nice

assert_eq(ddf, pdf, sort_results=False)
10 changes: 9 additions & 1 deletion dask/dataframe/utils.py
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Expand Up @@ -261,7 +261,7 @@ def strip_unknown_categories(x, just_drop_unknown=False):
return x


def clear_known_categories(x, cols=None, index=True):
def clear_known_categories(x, cols=None, index=True, dtype_backend=None):
"""Set categories to be unknown.

Parameters
Expand All @@ -273,7 +273,15 @@ def clear_known_categories(x, cols=None, index=True):
index : bool, optional
If True and x is a Series or DataFrame, set the clear known categories
in the index as well.
dtype_backend : string, optional
If set to PyArrow, the categorical dtype is implemented as a PyArrow
dictionary
"""
if dtype_backend == "pyarrow":
# Right now Categorical with PyArrow is implemented as dictionary and
# categorical accessor is not yet available
return x

if isinstance(x, (pd.Series, pd.DataFrame)):
x = x.copy()
if isinstance(x, pd.DataFrame):
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